feat(FN-3025): add agent onboarding flow with launch gating

- Add backend onboarding session service and legacy API routes for start, state, and import/export generation
- Introduce experimental AgentOnboardingModal UI with stream-state handling, model selector wiring, and onboarding launch flow in AgentsView
- Add onboarding gating via prompt overrides/store updates and include search behavior fix for partial-match filtering
- Expand dashboard/core tests for onboarding API, modal behavior, agents/settings integration, and prompt override handling

Fusion-Task-Id: FN-3025

packages/dashboard/src/__tests__/agent-onboarding.test.ts

@@ -0,0 +1,75 @@
+import { describe, it, expect } from "vitest";
+import {
+  parseAgentOnboardingResponse,
+  createAgentOnboardingSessionPrompt,
+} from "../agent-onboarding.js";
+
+describe("agent-onboarding", () => {
+  it("parses question responses", () => {
+    const parsed = parseAgentOnboardingResponse(
+      JSON.stringify({
+        type: "question",
+        data: {
+          id: "q1",
+          type: "text",
+          question: "What should this agent focus on?",
+        },
+      }),
+    );
+
+    expect(parsed.type).toBe("question");
+    if (parsed.type === "question") {
+      expect(parsed.data.id).toBe("q1");
+    }
+  });
+
+  it("parses complete summary responses", () => {
+    const parsed = parseAgentOnboardingResponse(
+      JSON.stringify({
+        type: "complete",
+        data: {
+          name: "Docs Reviewer",
+          role: "reviewer",
+          instructionsText: "Review docs for clarity and accuracy.",
+          thinkingLevel: "medium",
+          maxTurns: 20,
+        },
+      }),
+    );
+
+    expect(parsed.type).toBe("complete");
+    if (parsed.type === "complete") {
+      expect(parsed.data.name).toBe("Docs Reviewer");
+      expect(parsed.data.maxTurns).toBe(20);
+    }
+  });
+
+  it("rejects invalid complete summary", () => {
+    expect(() =>
+      parseAgentOnboardingResponse(
+        JSON.stringify({
+          type: "complete",
+          data: {
+            name: "",
+            role: "reviewer",
+            instructionsText: "",
+            thinkingLevel: "medium",
+            maxTurns: 0,
+          },
+        }),
+      ),
+    ).toThrow(/Invalid summary/);
+  });
+
+  it("builds compact onboarding context prompt", () => {
+    const prompt = createAgentOnboardingSessionPrompt({
+      intent: "Need a reviewer for docs",
+      existingAgents: [{ id: "a1", name: "Alpha", role: "reviewer" }],
+      templates: [{ id: "t1", label: "Reviewer Template", description: "General reviewer" }],
+    });
+
+    expect(prompt).toContain("Need a reviewer for docs");
+    expect(prompt).toContain("a1:Alpha(reviewer)");
+    expect(prompt).toContain("t1:Reviewer Template");
+  });
+});